Field of view calibration for modular nuclear medical imaging system

Abstract

A method and apparatus for correcting misalignment between fields of view of a CT device and a NM device of a modular multimodality medical imaging system, by providing a Field Of View Calibration Matrix (FOV-CM) containing rotational and translational transformations between coordinate systems of the CT and NM systems.

1. A method for correcting misalignment between a computed tomography (CT) image and a nuclear medical (NM) image in a modular multimodality imaging system, comprising:
 identifying a difference between an NM patient coordinate system (PCS) with respect to a CT PCS by applying a field of view calibration matrix (FOV-CM) comprising a rotational transformation and a translational transformation of a spatial point that exists in both the NM PCS and in the CT PCS, and 
 aligning the CT image and the NM image based on the difference, and performing a cardiac reconstruction with attenuation correction by adjusting the CT PCS to match the NM PCS, calculating an attenuation map, performing a reconstruction based a CT attenuation map slice, applying the FOV-CM to form an NM reconstruction volume in CT-PCS, rotating, shifting, and masking the NM reconstruction volume in CT-PCS to create an image of standard cardiac orientation, wherein the steps above are performed using at least one processor. 
 
     
     
       2. The method according to  claim 1 , wherein the FOV-CM is generated by measuring the positions of three non-collinear points. 
     
     
       3. The method according to  claim 1 , wherein the FOV-CM is generated by subtracting two CT image sets to remove background structures and to isolate point images, and calculating positions of the point images. 
     
     
       4. The method according to  claim 1 , further comprising rebinning the CT image based on location, orientation, matrix size, and pixel size of the NM image. 
     
     
       5. A modular imaging system comprising:
 a programmable element for correcting misalignment between a computed tomography (CT) image and a nuclear medical (NM) image in, the programmable element programmed to identify a difference of an NM patient coordinate system (PCS) with respect to a CT PCS by applying a field of view calibration matrix (FOV-CM) comprising a rotational transformation and a translational transformation of a spatial point that exists in both the NM PCS and in the CT PCS, and to align the CT image and the NM image based on the difference, wherein the programmable element is further programmed to perform a cardiac reconstruction with attenuation correction by adjusting the CT PCS to match the NM PCS, calculating an attenuation map, performing a reconstruction based a CT attenuation map slice, applying the FOV-CM to form an NM reconstruction volume in CT-PCS, rotating, shifting, and masking the NM reconstruction volume in CT-PCS to create an image of standard cardiac orientation. 
 
     
     
       6. The system according to  claim 5 , wherein the programmable element further programmed to generate the FOV-CM by measuring the positions of three non-collinear points. 
     
     
       7. The system according to  claim 5 , wherein the programmable element is further programmed to generate the FOV-CM by subtracting two CT image sets to remove background structures and to isolate point images, and calculating positions of the point images. 
     
     
       8. The system according to  claim 5 , wherein the programmable element is further programmed to rebin the CT image based on location, orientation, matrix size, and pixel size of the NM image.